An aneurysm is a medical condition indicated generally by an expansion and weakening of the wall of an artery of a patient. Aneurysms can develop at various sites within a patient's body. Thoracic aortic aneurysms (TAAs) or abdominal aortic aneurysms (AAAs) are manifested by an expansion and weakening of the aorta which is a serious and life threatening condition for which intervention is generally indicated. Existing methods of treating aneurysms include invasive surgical procedures with graft replacement of the affected vessel or body lumen or reinforcement of the vessel with a graft.
Surgical procedures to treat aneurysms can have relatively high morbidity and mortality rates due to the risk factors inherent to surgical repair of this disease, as well as long hospital stays and painful recoveries. Due to the inherent risks and complexities of surgical repair of aortic aneurysms, endovascular repair has become a widely used alternative therapy, most notably in treating AAAs. Early work in this field is exemplified by Lawrence, Jr. et al. in “Percutaneous Endovascular Graft: Experimental Evaluation”, Radiology (May 1987) and by Mirich et al. in “Percutaneously Placed Endovascular Grafts for Aortic Aneurysms: Feasibility Study,” Radiology (March 1989). Commercially available endoprostheses for the endovascular treatment of AAAs include the Endurant® stent graft system manufactured by Medtronic, Inc. of Minneapolis, Minn., the Zenith® stent graft system sold by Cook, Inc. of Bloomington, Ind., the PowerLink® stent graft system manufactured by Endologix, Inc. of Irvine, Calif., and the Excluder® stent graft system manufactured by W.L. Gore & Associates, Inc. of Newark, Del. A commercially available stent graft for the treatment of TAAs is the TAG™ system manufactured by W.L. Gore & Associates, Inc.
Aneurysms and the like in the vasculature are a condition manifested by expansion and weakening of the walls of one or more vessels of the vasculature. Such conditions require intervention due to the severity of the sequelae. Methods of treating aneurysms have included invasive surgical methods with placement of a vascular graft within a vessel as a reinforcing member thereof. However, such a procedure requires a surgical cut of the vessel for access thereto which, in turn, can result in a rupture of the aneurysm due to the decreased external pressure from the organs and tissues surrounding the vessel, which are moved during the procedure to gain access thereto. Accordingly, surgical procedures have disadvantages due to the possibility of the rupture of the aneurysm in addition to other factors. Such other factors can include a declined physical condition of the patient due to blood loss, anuria, and low blood pressure associated with the aneurysm.
Aneurysms may occur in a section of the vessel near a central section thereof from which one or more branch vessels extend. A vascular graft that is deployed in a section of the vessel near the central section preferably accommodates such one or more branch vessels by providing for the flow of blood that is within the graft into the branch vessels as would occur in the absence of the graft. Also, the vascular graft preferably provides for the flow of blood that is within the branch vessels into the central section also as would occur in the absence of the graft.
An aneurysm located near one or more branch vessels may result in a graft landing zone in the aneurysm's central section that has a relatively short axial length for supporting the vascular graft. Consequently, providing a seal between the vascular graft and central section in this landing zone may be difficult. Such a seal is advantageous to obstruct the flow of blood from the branch vessels through an annular clearance which may be present between the vascular graft and central section to the aneurysm. Preventing the flow of blood into the aneurysm is advantageous since the aneurysm is a weakened section of the wall of the vessel and, consequently, normally has limited capability to contain blood therein.